1. Field of the Invention
The present invention relates to a spindle control system for a numerical control apparatus, and more particularly, to a spindle control system in which a contour control is carried out by a spindle.
2. Description of the Related Art
Contour control by a spindle is conducted while controlling the position of the spindle, to carry out a complicated grooving or machining of a cam, etc., when using a lathe or the like. A prior art system for carrying out the spindle contour control uses a contour control servomotor, and a clutch for connecting the spindle to a spindle amplifier for spindle rotation or to the contour control servomotor.
The prior art system, however, requires a special servomotor for controlling a spindle motor, and a clutch or the like for a changeover between the spindle motor and the servomotor, and thus the entire system has a complicated structure.